In Nomine Patris Et Filii Et Luna Maledictae
by Pentakill Lux
Summary: Stiles is a Demon. So what if it's not really something he feels compelled to announce to the world, why should he have to? The boy who sleeps inside of him was dying anyway and no one is getting hurt. In fact, Stiles thinks, most people are benefiting a lot from this arrangement. Even if they'll never know. Demon!Stiles. Spoilers for aired episodes.
1. Chapter 1

Title means: In The Name Of The Father And The Son And The Cursed Moon.

Fic inspired by a prompt on Tumblr: Stiles has been a decently good-natured demon this entire time, possessing the body of a kid who would have otherwise died already. Stiles is still Stiles, he just happens to be a demon.

* * *

There was sunshine and wind and a myriad of sounds and for the first time Stiles felt something that wasn't hate.

Hell was full of hate. Fear, pain and hate. Earth was so different it was overwhelming.

If Stiles focused his essence he could even taste it, the happiness and peace - it was intoxicating in a way Stiles had never imagined, but also surprisingly exhausting. So in the end Stiles sought out the one place that didn't emit life and joy: The Beacon Hill hospital.

It was here he found the man. He was asleep, slumped across the dying body of a woman. Stiles could feel the sorrow and pain and guilt and it felt like home. This would be his vessel. This man. He would lose his wife soon - it was a matter of hours - and then he would be alone.

"Dad?"

Stiles whirled around in the shadows, essence reaching out to examine the new human in the room. It was a child - a boy - and he too was dying, even if the sickness in him was far less progressive. He would live a while yet, even if death for him was as certain as it was for the woman. The child's mother, Stiles reasoned. Well, that changed things. Stiles had not come here to make orphans.

A nurse walked in, emitting waves of busy determination. "Mr. Stilinski, go home and sleep, please? Your son needs a real meal and his own bed. She'll be asleep until tomorrow and we'll call you if there are any changes."

Stilinksi? Well, that was just too convenient. And right at that moment Stiles made his choice. It would have to be the boy. Stiles couldn't cure him, but he could keep him alive, let him have a dormant existence and keep his dad happy.

That night Mr. Stilinski told his son to go get ready for bed and while the boy brushed his teeth the father washed tears out of his eyes in the kitchen sink.

The boy had the warmest soul Stiles had ever met, but of course Stiles had mostly dealt with sinners. This boy was pure and full of love and it took a while to settle in and adjust to the new confinements and the effect the boy's soul had on Stiles' essence.

"I'm sorry I fell asleep on you in the hospital, son. I promise I'll give you more attention now." Mr. Stilinski sat down on the bed. "You know I love you, right?"

"I know, dad." Stiles said and the action was new and took some getting used to. But he liked it - liked saying words. "I'm gonna be Stiles from now on." Stiles said and the man - his new father - smiled a sad little smile.

"Is it because you're mad at your mom? You know this isn't her fault? You know how much she loves you, right?"

"I know." Stiles said and reached out to take his dad's hand. It was shaking, but warm. "And it's not because mom named me. I'm not mad at her, it's just… I don't want to always be reminded."

"Well, Stiles." His father said and let his free hand run through Stiles short hair. "If that's what you want."


	2. Chapter 2

Stiles' vessel is 12 when he realizes how stupid he's been. Humans grow. Stiles does not.

It doesn't take an incredible street smart demon(and yes that's exactly what Stiles is) to figure out that he's got a problem keeping up his little charade.

This is not really a thing he can plan around. He watches as the kids around him grow taller and older. He watches as the boys become gangly teens and the girls start growing breasts. Well, he doesn't watch in a creepy way, obviously, but it does help ones possibilities for observation to be able to teleport around town and hide in the shadows.

Stiles estimates that he has another year, if that, before he'll have to find a new vessel. The boy will die, but there is nothing Stiles can do about that now. He's been living on borrowed time anyway and Stiles has to look out for his own ass first. A boy who never grows older attracts too much attention.

But that winter everything changes.

Winter is the best time of year. Humans sweat less at winter, oh good grief, the sweating. Stiles will never get used to all these annoying bodily fluids. Of course winter has snot, but humans are generally polite enough to keep that to themselves. Stiles' body, of course, does none of these things, which is probably the only plus side there is to it because it's confining and restricting and - well _scrawny_.

But life on earth hurts a little less when you're protected by human skin; the sun doesn't burn as much and the multitudes of chemical and emotional impression that whirl around him is also dampened by the human's weak senses.

But oh yeah, that winter. Stiles had to adopt much of the boys personality when he took over the body. Usually demons didn't have to, because "fitting in" isn't really their main priority, but for Stiles it was necessary. There were memories and emotions too and Stiles wondered if all humans were this... Earnest? Passionate? Looking for word... _Sappy_. That's the one!

The boys memories clung to his parents, which was hardly a surprise. With all that human being was accused of being throughout time, sentimental was perhaps the most apt description. But there was also the girl. Lydia Martin.

She was plain, even as far as humans goes, red hair and pale skin. Average intelligence and no special courage to talk of. As far as Stiles could see the boy's obsession had started with the girl having a pretty smile. As noted above, _sappy_.

But that winter Stiles would come to understand just how powerful human emotions could be.

It had snowed. Crystallized water at it finest. Unless you count ice-sculptures, of course. Stiles once knew an erotic ice sculptor who carved this huge... well, it was grand and not very lifelike, one might add.

The frost had gone deep already, freezing lakes and streams solid and the kids of Beacon Hill were all outside. Apparently, it was frowned upon to engage in fistfights most of the year, but as soon as snow was involved it was perfectly legal to throw lumps of ice at other kids, roll them in the snow and then laugh. This fact alone might have doubled Stiles fondness for winter.

Lydia Martin was outside too, but she was dancing on the lake. Stiles felt a tug at his heart at the beauty of it and he knew it came from the boy inside.

With blades strapped to her feet she twirled and glided in elaborate patterns that was only in her own head. Stiles kept watching. Even after it grew darker and most of the kids went home he stayed to watch her preform. She was lost in her own head and the patterns became even more eerie and hypnotic.

And that was when the ice broke. Loudly and sudden, sending the girl into water so suffocating and cold that she couldn't even scream.

Stiles wasn't going to save her. There were still children there, watching and panicking as humans do, but they would notice if he was suddenly there out of nowhere, to pull her out of the black water. But then the boy inside reacted.

It was a demand so profoundly strong that Stiles almost lost control of the body for a fraction of a second, but it was frighting enough to send Stiles running for the hole in the lake where Lydia Martin had disappeared, sliding into the water as kids around him screamed.

The cold water had no effect on Stiles, but he knew humans were fragile and when he surfaced with the girl in tow she was lifeless. But the boy inside was relentless. _Save her, save her now!_

Stiles didn't have healing powers. A demon saving a human was outrageous, it couldn't be done. It had happened from time to time that demons had mended another demon with their essence, but humans were so different, all flesh and goo and sticky bits.

_Do it, save her!_

Well, Stiles thought, here goes nothing. Or even less than nothing, actually, because there was no way in hell it could possibly... oh shit, it was working!

Stiles could feel his essence splitting and it was painful and scary, but it was working. Cells, popped by the cold like rice krispies, morphed into a state that wasn't quite healed, but not quite broken either. It was the same emergency patch up that demons used on their own vessels to keep the body from rotting and bleeding out as long as they were still inside them, but Stiles knew it would only hold as long as some of his own essence stayed behind.

_Do it! Keep her alive_, the boy demanded and Stiles told him to shut up. This was walking on thin ice, pun intended, because it would mean that the Martin girl would be different. Not quite human, but not quite anything else either. She'd be stronger, smarter and better, but not so much that anyone would be able to call her a freak for it.

And we'll be weaker, Stiles told the boy inside. We won't be as powerful. We'll be open to attacks, be killable. We'll get sick and we'll - oh, we'll_age_.

_It's worth it_, the boy said and Stiles should have gotten out right then and there, because nothing in the world was worth dying for. _Nothing_. But Stiles couldn't get out. He was already in too deep, caught in the dad's brave attempts at keeping face in front of his kid while he was drowning inside in guilt and sorrow. Caught by the boy inside, his kindness and willingness to sacrifice himself for these random and brief creatures around him.

Stiles knew that if they could make it through alive and keep the Martin girl alive too, then Stiles could simply take his essence back later and be whole again, be immortal again. All he had to do was keep them alive.

And Stiles would age, the charade would be complete and he would be able to stay.

I'll do it, he told the boy and with those words everything changed.


	3. Chapter 3

Stiles is 14 when his father gives in and gets him a Boa.

Stiles has always been fascinated with serpents. Maybe it's because Lucifer has always been affiliated with this particular animal. And really, Stiles sees why. The way they're cold and calculated; how they are content to lie in waiting, striking the perfect blow when the time is right.

Stiles feeds it live mice until his father catches him and tells him off - something with animal cruelty and probably some rules and regulations; Stiles isn't listening. He tells his dad that the order of predator killing its food is the most primal and natural in the world and that the mouse is actually lucky to get to be a part of a ritual that's almost as old as life itself. After that his father takes the snake back to the pet store. Stiles does his best not to throw a tantrum.

That's when Stiles realizes that he still has a lot to learn about humans.

Stiles' dad is a bad representation of the human species, that much is clear. Despite the general self-torturing disposition of most humans, few people in Beacon Hill harbor as much pain and sorrow as the Sheriff does. The only thing Stiles learns from his human dad is how to get up in the morning and pretend you're okay.

And Lydia is an even worse representation as she is now almost as cold as the snake. Stiles made sure Lydia never found out who saved her life, even though the boy inside protested violently. The cover came first and Lydia would be safer if she wasn't connected to Stiles in any way. That did not stop the boy inside from pining after her, but Stiles controls him, mostly.

That's when he finds Scott.

Scott has asthma and low self-esteem. He lives alone with a mother that works too much. He loves computer games, tacos and his job at the animal clinic and most importantly he's kind, loyal and caring and he gives Stiles the unique opportunity to study a human up close. He might not be the brightest kid, but then Stiles is smart enough for the both of them.

He tries his best not to corrupt Scott too much. It's hard though, because Stiles is what he is and mischief, adventures and liberal amounts of sarcasm is a part of that. But luckily Scott is a far better person than his old man ever was and he tolerate Stiles with a soft smile and an incorruptible love. And that's how the two of them knit together.

Scott: "Let's make dinner for our parents and try to get them together."

Stiles: "Let's stay up all night and play Doom."

Scott: "Let's try out for the Lacrosse Team."

Stiles: "Let's go out in the woods and look for half a dead body."

And then suddenly Scott isn't human anymore.

Which, sure, makes him more entertaining, but it kinda takes the whole _"I'll make a man out of you!"_- element out of their friendship. Not that Stiles actually minds so much; he's getting to a point where he's past the Humans 101 anyway. Werewolves could be a fun new twist albeit not one he expected to encounter in sleepy Beacon Hill.

Maybe that's why it takes him a while to make the connection between Scott's solo adventure in the woods and his new skills on the Lacrosse field. Because, yes, Stiles _knows_ about werewolves. He's old after all, and not in the creepy decaying sort of way that humans grow old. He's a demon in his best age. Pyramids of Egypt? He totally help build those suckers.

Humanity never changes though, not _one bit_ since last time Stiles was on the surface. And even though he never bothered finding out what makes mankind tick, he knows one thing: They always enjoyed inventing things that go bump in the night. Easier to be scared of things that aren't real than deal with the monsters that are. Last time Stiles was on earth there were talk of dragons and centaurs. Those, by the way? Aren't real. Werewolves? Well, one little curse gone wrong and _furries_ are walking amongst us, who knew?

Scott, of course, takes his new "gift" in stride, apart from the freaking out and going running in the woods half naked. When the wolf takes over you're all about instincts and connecting with your animal side. And that is bad for Scott, because there aren't many good things to say about his intellect as a human and his wolf-side is about three feeble brain cells away from being unable to control its drool.

Enter Derek Hale, the prodigal son returning to Beacon Hill with a major in advanced self loathing and brooding.

Stiles recognizes him right away, even though the demon had been fresh out of Hell the last time he saw the kid. Derek had been a relatively happy teen back then, normal and well adjusted, even. Stiles has to admit, although grudgingly, that he hadn't picked up on the whole werewolf vibe back then. Derek and the rest of the Hales had seemed like your ordinary upper class family. That was before the fire though, and Stiles hadn't thought about the kid since.

The thing is, the kid isn't a kid anymore. He's all grown up in all the right places and Stiles may or may not be staring like the horny teen he's supposed to be, until he remembers that Derek Hale is a creature of the night who could theoretically whoop Stiles cute ass now.

Stiles sometimes forgets he's not all powerful anymore. The first time he got hurt and bled was… _new_. He heals fine, maybe a bit faster than normal humans, but it's still annoying. Having to eat is also a nuisance(only made easier by the existence of burgers), not to mention getting it out again! He had to give up teleporting as well, relying completely on the Jeep his dad gave him. It's slow, but so is most of human life.

So yeah, adding werewolves to the dull hum of human life is like adding booze to your milkshake and Stiles isn't even embarrassed to admit that he's enjoying himself at first.

The problem with werewolves, though? They tend to bring hunters to the yard, much like said milkshake.

Hunters have been around since mankind. They used to be men with pointy sticks, but lucky for them there were people smart enough to invent and arm them with more advanced gadgets as time passed. Well, some of them still use pointy sticks - it all depends on what they're hunting.

Werewolf hunters weren't necessarily the brightest bunch. The creatures they hunted were brutal and ferocious, but not big on strategics. (Not like Demon hunters, who were hunting the smartest, most cunning and savvy things ever created.)

So it's not that Stiles fears for himself, because let's face it: no one is going to be looking for a demon in the middle of a wolf pack. But there is one human that Stiles would lay down his life to protect, though. A silly, ordinary human girl who just happens to contain half of Stiles precious essence, making her not only smarter and better, but also the most valuable human being in existence. And that girl just have to go and make friends with Allison _Argent_.

If it wasn't for Scott's inexplicably lack of self preservation, making him fall in love with the Argent girl, Stiles wouldn't even have known that the Argents were hunters until it might have been to late.

Because the Argents are smart and organized and not like any werewolf hunters Stiles have ever encountered before. And they also happen to be deadly and Stiles doesn't want them anywhere near Lydia Martin. Once again, however, Lady Luck smiles at Stiles and Allison Argent decides, for what ever reason, that Scott is interesting and _sweet_. What could have been a terrible, bloody car crash turns out to be a door into Lydia Martins inner circle.

He should, if he had any kind of common sense, take his essence from Lydia and get the hell out of Beacon Hill. But apparently common sense isn't that common and although Stiles would like to pretend that he's cold and calculated, that he can pick up and leave when he wants to, evidence doesn't lie.

The day he merged with the boy inside he bound himself to Beacon Hill. He can't abandon Scott to Derek and the hunters any more than he could abandon Papa Stilinski to his drunken sorrow or Lydia Martin to the cold darkness under the ice.

But the thing that keeps him around in the end is the boy inside and his silent, persistent pleas: _Please don't go. She'll die without your essence. Please don't let her die._

Not once does the boy beg for his own life.


End file.
